I. Field of the Invention
The present invention generally relates to devices, systems, and methods for diagnosing and/or treating of the heart. In a particular embodiment, the invention provides techniques for localizing and/or treating atrial fibrillation and other arrhythmias.
Significant progress has recently been made toward effective treatments of many cardiac arrhythmias. Contraction of a healthy human heart generally propagates through the heart tissue from the sinus node in the right atrium, and eventually the associated ventricles. This normal propagation of contraction forces blood to flow from the atria to the ventricles in a synchronized pumping action. Focal or re-entrant arrhythmias of the heart often originate at, and propagate from alternative heart tissue locations, resulting in irregular contractions of some or all of the heart tissues. Radiofrequency intracardiac catheter ablation of the alternative ectopic origin is now used to effectively treat a variety of arrhythmias, including ventricular tachyeardia (VT).
Although quite effective, current catheter ablation of arrhythmogenic sites has significant disadvantages. A particular challenge in an effective catheter ablation treatment is the time required for proper identification of the treatment site. As it is generally desirable to limit the size of the ablation, significant time is often spent testing candidate ablation sites. These candidate sites are often tested sequentially by positioning the intracardiac catheter against a site within (for example) the right ventricle, identifying the engaged tissue location within the ventricle, sensing and/or pacing the heart at the candidate site, repositioning the intracardiac catheter to a new candidate site, and repeating this process until the ectopic origin has been identified.
As fluoroscopy is often used to identify the location of the engaged tissue, this sequential iterative process can result in significant exposure of the patient and treating personnel to potentially harmful radiation. While alternative (and more complex) intracardiac catheter probe structures have been proposed to allow more rapid identification of the ectopic origin(s) of VTs and other focal arrhythmias, the size and cost of these complex structures may limit their acceptability, particularly for treatment of (for example) the left atrium of the heart, which is often accessed from the right atrium by a puncture through the atrial septum.
To overcome the disadvantages associated with these known time consuming and/or invasive intracardiac arrhythmia sensing and localization techniques, researchers have been working on alternative arrhythmia localization techniques which rely on body surfacing mapping often during pacing. Pacing often comprises initiating the arrhythmia by applying a small electrical pulse from a catheter. Electrocardiograms (ECG) may be recorded during abnormal atrial or ventricular activity and compared with ECGs taken during pacing at different sites within the heart, optionally using a standard 12-lead ECG system. More detailed information regarding ectopic sites can be obtained by recording heart cycle signals at the body surface using a more comprehensive sensor array. These heart cycle signals, which generally comprise small amplitude variations in electrical potential along the anterior and/or posterior torso, can be manipulated and/or mapped so as to provide an indication of the origin of the arrhythmia within the heart. Much of this work has concentrated on VT. More recent work has begun to investigate the possibility of localizing certain atrial arrhythmias, such as right atrial tachycardia. While the initial results of this research appear quite promising for treatment of selected individuals, significant advancements would be beneficial to allow widespread treatment of patients suffering from cardiac arrhythmias.
The most common form of cardiac arrhythmia may be atrial fibrillation (AFib). Atrial fibrillation is often paroxysmal in nature, which may contribute to the significant risks of the disorder. Atrial fibrillation may result in twice as many hospitalizations annually as VT, and may cause significant morbidity and/or mortality, leading not only to heart failure, but associated risks of thrombo-embolism and stroke.
Many current AFib patients are managed using antiarrhythmic drugs. Unfortunately, existing drug treatments are merely palliative, since they are aimed at suppression of the arrhythmia and not at curing the underlying disease. Many researchers are directing resources to development of therapeutic catheters to treat atrial fibrillation, attempting to build on several years of successful ablation for treatment of other arrhythmias. Early indications are that when accurately identified, ablation of ectopic origins of focal AFib may provide an effective treatment for the disorder. Hence, there would be significant benefits to extending the new body surface localization techniques to atrial fibrillation. The nature of AFib, however, represents a significant barrier to the direct application of known mapping techniques used with other arrhythmias.
Atrial fibrillation is generally more complex and difficult to localize than other arrhythmias. Focal AFib often exhibits an infrequent, irregular occurrence, and may be difficult to induce with known catheter mapping techniques. Even when atrial fibrillation is ongoing and/or successfully induced in the lab, AFib may exhibit prolonged occurrences in many patients, possibly requiring repetitive direct current shock cardioversion to convert the patient back into a normal sinus rhythm. Atrial fibrillation may also have multiple focal arrhythmia sources, possibly leading to detailed catheter mapping and unacceptably long procedures. Procedure times in general may be excessively long, particularly when conducted under prolonged fluoroscopic imaging, leading to excessive x-ray exposure to the patient, physician, and nursing staff. The current invasive options for AFib mapping also have significant disadvantages, particularly when they involve extended and/or traumatic catheter manipulation in the left atrium.
In light of the above, it would be desirable to provide improved devices, systems, and methods for localizing and/or treating AFib and other arrhythmias within a heart of a patient. The present invention provides such improvements, mitigating and/or overcoming at least some of the disadvantages of known approaches for diagnosing and treating arrhythmias.
II. Related Art
The following patents may be relevant to the subject matter of the present invention, and their full disclosures incorporated herein by reference: U.S. Pat. No. 5,311,873; and U.S. Pat. No. 5,634,469. Peeters, H. A. P., SippensGroenewegen, A. and others described xe2x80x9cClinical Application of an Integrated 3-Phase Mapping Technique for Localization of the Site of Origin of Idiopathic Ventricular Tachycardiaxe2x80x9d in Circulation, 99:1300-1311 (1999). SippensGroenewegen, A. et al. also described xe2x80x9cBody Surface Mapping of a trial Arrhythmias: Atlas of Paced P wave Integral Maps to Localize the Focal Origin of Right Atrial Tachycardiaxe2x80x9d, in J. Electrocardiol., 31(Supp.):85-91 (1998). Related work was described by SippensGroenewegen, A. et al. in, xe2x80x9cValue of Body Surface Mapping in Localizing the Site of Origin of Ventricular Tachycardia in Patients with Previous Myocardial Infarctionxe2x80x9d, J. Am. Coll. Cardiol. 24:1708-1724 (1994). Each of these references is incorporated herein by reference.
The present invention provides improved devices, systems, and methods for localizing and/or treating arrhythmias of a heart. The techniques of the present invention are particularly useful for localizing atrial fibrillation, and allow locating arrhythmogenic regions of a chamber of the heart using heart cycle signals measured from a body surface of the patient. Non-invasive localization of the ectopic origin allows focal treatment to be quickly targeted to effectively inhibit these complex arrhythmias without having to rely on widespread and time consuming sequential searches, and/or on massively invasive simultaneous intracardiac sensor techniques. The invention recognizes that effective localization of these complex arrhythmias can be significantly enhanced by techniques and structures which separate superimposed heart cycle signals originating from differing chambers and/or regions of the heart tissue. In the exemplary embodiment, P wave signal portions are separated from superimposed QRST wave complex signals so as to isolate signals originating in an atrium from concurrent activity in the ventricle. The P wave signals may be measured by a thoracic array of electrical sensors distributed along the patient""s skin across the torso. The invention allows invasive pace-mapping to be limited to a predetermined arrhythmogenic region within a particular chamber of the heart, often followed by ablation of the ectopic origin to inhibit the arrhythmia.
In a first aspect, the invention provides a method for treating fibrillation in a heart of a patient. The patient has an exposed body surface, and the method comprises measuring the fibrillation from the body surface. An arrhythmogenic region of the heart is located in response to the measured fibrillation. Treatment is directed at or near the arrhythmogenic region so that fibrillation is inhibited.
Preferably, heart cycle signals are sensed while no intracardiac probe is present in the heart, with the arrhythmogenic region being determined (at least in part) using the non-invasively sensed heart cycle signals. In many cases, an array having more than about 20 sensing locations will be coupled to thoracic skin of the patient. The sensed heart signals will often include signals originating in an arrhythmogenic chamber of the heart, superimposed with signals from other chambers. Typically, an atrial signal will be superimposed with a ventricular signal. These superimposed signals are separable by signal separators. The methods of the present invention often include separating the atrial and ventricular signals with such a signal separator.
In the exemplary embodiment of the present method, at least one reference cycle is selected from among a plurality of heart cycles measured by the sensor array. The arrhythmogenic region can be determined from the measured signals during this reference cycle, typically by selecting a time portion of the reference cycle, by integrating the separated signals from each sensor location within the selected time portion, and by arranging the resulting integral values within a data matrix according to the locations at which the signals are sensed along the body surface. Such a data matrix may be graphically plotted with the plots often including lines of constant integral values. These plots can be used to identify the arrhythmogenic region, most commonly by comparing the data matrix and/or plots to a database having a plurality of known arrhythmia cycles. Such databases will often have associated known arrhythmogenic regions for each known arrhythmia cycle.
Advantageously, the locating of the arrhythmogenic region can be performed using measurements of spontaneous fibrillation. The located arrhythmogenic region may have a surface area of less than about five square centimeters, often having an outer radius of less than about 2.5 cm, and ideally having an outer radius of about 1.0 cm or less. An ectopic site or exit site within such a limited arrhythmogenic region may be more precisely identified by subsequently introducing a mapping/pacing probe into the arrhythmogenic atrium. Alternatively, where locating can be performed to sufficient accuracy solely using the sensor array, ablation may directly proceed based on the non-invasively identified arrhythmogenic region. Such ablation will often be performed using radiofrequency energy, cryogenic cooling or electrosurgical energy, buy may alternatively be effected by focal or circular delivery of cryogenic cooling, ablative compounds, ultrasound energy, microwave energy, laser energy, or the like. Circular or perimeter lesions may be particularly beneficial for isolating arrhythmogenic regions in or near pulmonary veins and the like.
In another aspect, the invention provides a method for treating arrhythmia in a heart of a patient. The patient has an accessible body surface, and the heart has a left atrium, a left ventricle, a right atrium, and a right ventricle. Heart signals at the body surface include atrial signals superimposed with ventricular signals. The atrial and ventricular signals are separable by a separator. A database has information regarding a plurality of known arrhythmia cycles, each known arrhythmia cycle having an associated known arrhythmogenic region. The method comprises sensing signals during an arrhythmia initiation cycle from the body surface. Alternatively, one can also sense premature atrial beats with focal AFib, and/or persistent AFib. The atrial signals are separated from the sensed signals with the signal separator. An arrhythmogenic region (or in some embodiments, an insertion point of a concealed accessory pathway) of an atrium of the heart is located by comparing the separated signals to the database. A treatment is directed at or near an ectopic site or exit site within the arrhythmogenic region so that the arrhythmia is inhibited.
In another aspect, the present invention provides a system for treating arrhythmia in a heart of a patient. The patient has an accessible body surface and the heart has an atrium and a ventricle. A sensor array can be coupled to the body surface for sensing heart signals, the heart signals including atrial signals superimposed with ventricular signals. The atrial and ventricular signals are separable by a signal separator. A database includes information regarding a plurality of known cycles, each known arrhythmia cycle having an associated arrhythmogenic region. The system comprises a processor coupled to the sensor array and the database. The processor derives an arrhythmogenic region of the atrium from the heart cycle signals by separating the atrial and ventricular signals with the signal separator, and by comparing the separated signals to the database. A probe directs focal treatment at or near the arrhythmogenic region so that the arrhythmia is inhibited.
In yet another aspect, the invention provides a kit for use with a probe and a sensor array to treat arrhythmia in an atrium of a heart of a patient. The sensor array is coupleable to the body surface for sensing heart cycle signals. The probe has a treatment delivery surface. The kit comprises a processor coupleable with the sensor array. The processor generates an output in response to sensed heart cycle signals from the array. The kit also includes instructions for locating the arrhythmogenic region within the atrium by sensing the heart cycle signals from the body surface when no intracardiac probe is present in the heart, and by comparing the output of the processor with the database.
In yet another aspect, the invention provides a system for localizing an arrhythmia. The system comprises an input for body surface signals and a processor coupled to the input. The processor derives an arrhythmogenic region of a heart in response to the body surface signals. An output graphically indicates the arrhythmogenic region.